What is refraction?
the fact or phenomenon of light, radio waves, etc. being deflected in passing obliquely through the interface between one medium and another or through a medium of varying density.
change in direction of propagation of any wave as a result of its travelling at different speeds at different points along the wave front.
measurement of the focusing characteristics of an eye or eyes (Murray et al., 1961).
Murray, J., Bradley, H., Craigie, W. and Onions, C. (1961). The Oxford English dictionary. 1st ed. Oxford: Clarendon Press.